CA1243516A

CA1243516A - Method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formation

Info

Publication number: CA1243516A
Application number: CA000390107A
Authority: CA
Inventors: Frank Calandra, Jr.
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-11-21
Filing date: 1981-11-16
Publication date: 1988-10-25
Also published as: GB2088509B; AU3763185A; DE3145824A1; AU564924B2; US4413930A; AU7742081A; GB2088509A; AU545538B2; DE3145824C2

Abstract

TITLE

METHOD AND APPARATUS FOR COMBINING RESIN
BONDING AND MECHANICAL ANCHORING OF A
BOLT IN A ROCK FORMATION
ABSTRACT OF THE DISCLOSURE

A mechanical anchor including an expansion shell and a camming plug positioned in the shell is threaded onto the end of a mine roof bolt. A roof support plate is carried on the opposite end of the bolt. The mechanical anchor is in-serted in a bore hole drilled in a rock formation with one or more resin cartridges advanced by upward movement of the bolt to the end of the bore hole. The cartridge is ruptured by upward thrust and rotation of the bolt to release the resin components for mixing. A stop device extending through the plug abuts a tapered end of the bolt to prevent axial movement of the plug on the bolt when the bolt is rotated in a pre-selected direction to mix the resin components before the shell is expanded. Rotation of the bolt continues without expansion of the shell for a period of time to permit formation of a curable resin mixture. As the resin mixture begins to harden rotation of the shell and plug is resisted until the stop device is displaced by the bolt tapered end permitting relative rotation between the plug and the bolt. The plug nonrotatably moves down the bolt upon continued rotation of the bolt in the same preselected direction to expand the shell into engagement with the wall of the bore hole before the resin mixture cures. The cured resin bonds the bolt and expanded shell to the rock formation to resist slippage of the expanded shell and maintain the bolt in tension.

Description

35~6 BACKGROU D OF THE It~VENTION

1 Field of the Invention , I
This invention relates to a method and apparatus for ¦ combining resin bonding and mechanical anchoring of a bolt in a I rock formation and more particularly to an expansion shell assembly adapted for use with bonding material where Mixing ox the bonding material components and expansion of the shell ¦ take place upon continuous rotation of the bolt in one rota-tional d irect ion .

2._ Description of the Prior Art It is well known in the art of mine roof support to tension bolts anchored in bore holes drilled in the mine roof to reinforce the unsupported rock formation above the roofO
Conventionally a hole is drilled through the roof into the rock ¦ ormation. The end of the bolt in the rock formation is anchored by either enga event of an expansion shell on the end Il .
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il I, Il X~Y'3 35~6 ¦¦ of the bolt with the rock formation or adhesively bonding the bolt by a thermosetting resin to the rock formation surrounding ¦ the bore hole. The resin also penetrates into the surrounding rock formation to adhesively unite the rock strata and to firmly hold the bolt in position in the bore hole. The resin mixture fills the annulus between the bore hole wall and the rod along a substantial length of the rod. With a conventional expansion shell it i5 also kllown to chamfer the end of bolt so that the threads on the end of the bolt that receive the expansion shell terminate at a point spread from the entreme end of the boltO This arrangement yrevents damage to the threads to permit recovery and reuse of the bolt.
¦¦United States Patents 3,324,66~ and ~,3~4,527 !I disclose adhesively bonding a rod positioned in a hole drilled ¦ in a rock formation by a thermosetting polyester resin compos-ition having thixotropic properties. It is well known that a bolt which is adhesively bonded in a bore hole can not be tensioned; on the other hand, a bolt mechanically anchored in a I¦ mine roof is capable of being tensioned but the contact of the ?~ roof bolt with the rock formation is confined to engagement oE
the expanded shell with the bore hole wall. Also, it lS well ¦ known that deterioration of the rock formation surrounding the expanded shell reduces the contact area between the shell and .

I1 129~35~ 1 the rock formation. Consequently the expanded shell slips and l i the tension on the bolt decreases, thereby reducing the roof l ;

! support. Slippage of a tensioned mechanical root bolt occurs most commonly in rock formations, such as shale, sandstone, ¦ mudstone, and the like. 3 ¦ In an attempt to resolve the disadvantayes of ¦ anchoring by resin bonding or anchoring by expansion shells l various types of mine roof support systems have been developea I that combine mechanical anchoring and resin anchoring 'l'he two 1¦ systems have been combined by threading a bolt into a separate member such as a nut or coupling which is attached to a "rebar"
anchored in the bore hole by a resin. bolt with a plate held against the surface of the mine roof surrounding the bore hole is threaded into the separate member. Tightening the bolt ¦ places the bolt under tension.
¦ United States Patent 3,702~060 discloses an expansion shell assembly that includes a resin container which is iixed to the end of an expander positioned within an expansion shell. The container is ruptured after the shell hegins to I expand. kotation of the bolt mixes the resin components, and the resin mixture surrounds the shell to embed the shell in the ¦I cured resin to bond the shell to the rock strata. Wnen the resin is fully cured, a nut on the end of the bolt opposite a 1l - 5 -!l 35~

roof plate on the bolt is rotated to hring the roof plate to its fully seated position against the mine roof to fully ! tension the bolt.
Combining bolt tensionillg and resin bondiny of a mine roof bolt bolt in the bore hole is disclosed in United States Patents 3,877,235 and 4,051,683. The devices disclosed in these patents utilize an internally threaded member such as a nut or coupling which is connected at one en to a "rebar"
l anchored within the bore hole by the mixed an cured resin. A
¦ bolt is then connected to the other end of the nut or coupling Il and includes a bearing or root plate advanced into abutting Il relation with the mine roof. stop means provided in the 'I coupling limits axial advancement of the bolt into the coupling to prevent relative rotation of the coupling and the bolt as the assembly is rotated to break the resin cartridge and mix the resin components. When the resin cures the "rebar" above tne coupliny is adhesively bonded to the rock formation.
Thereafter rotation of the bolt in the coupling fractures the stop means to permit the bolt to move upwardly in the bore hole so that sufficient torque is applied to the bolt to tension the bolt.

ll lZ'~3516 Similar devices which utllize a rocl anchored within the drill hole by resin bonding and connected to a bolt by a coupling with a stop device to restrain relative rotation between the members of the assembly until the resin hardens so that the bolt can be tensioned are disclosed in United States Patents 4,122,681 and 4,192,631. These devices rely upon the bonding of the elongated rod to the rock formation by the resin mixture. They do not utilize a mechanical anchor.
united States Patents 4,160,614 and 4,162,133 disclose a mechanical anchor in combination with resin bonding of the bolt and the rock fornlation. Rotatiorl of the bolt with I-the mechanical anchor attached to the end thereof in a first r directi.on effects mixing of the resin cormFonents of a ruptured cartridge. An anti-rotation device prevents relative rotation between the camming plug and the bolt so that the plug is not threaded off the end of the bolt during mixiny of the resin components. With this arrangement the resin components are thoroughly mixed before the shell is expanded. After a period of time sufficient for mixing the resin and before the resin hardens direction of rotation of the bolt is reversed 7 _ I
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to disengage the anti~rotation device. The camming plug is I¦ then free to advance downwardly on the bolt and expand the ! shell into gripping engagement with the wall of the bore hole.
The point anchor resin roof bolt support system utilizes the concept of anchoring a reinforcing rod in a mine , roof by resin bonding and tensioning the bolt. The rod is ¦ anchored at its upper en in the bore hole by resin. A nut is Il positioned on the threaded end of the rod that emerges from the

3 0 1l bolt hole and abuts a roof plate positioned in contact with the mine roof. The end of the rod at the nut is rotated to effect Il mixing of the resin. Rotation is terminated for a period of 30 to 60 seconds while the resin mixture cures. after the resin is set then the bolt is rotated at a preselected torque to tension the bolt.
While it has been suggested by the prior art systems I¦ to anchor a roof bolt in a bore hole by combination resin bonding and bolt tensioning where mechanical anchors have been used it has not been possible to mix the resin and set the anchor by continuous rotation of the bolt in one direction.

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" 5 With the known systems the bolt must be rotated in a first l direction to mix the resin while preventing expansion of the ¦ shell. When the mixed resin has begun to cure, when the direction of rotation of the bolt is reversed to expand the shell and set the anchor. Consequently careful attention must be given to rotating the bolt in the proper direction to mix the resin before the shell is set and not expand the shell before the resin is mixedO Furthermore when the bolt is rotated in the direction to effect mixinq of the resin, necessary means must be provided to prevent threhding the expander plug off the end of the bolt.
Therefore there is need in the system of combining resin bonding and mechanical anchoring of a bolt in a rock formation to provide a roof bolt anchor assembly that permits continuous rotation of a roof bolt in a single rotational direction to carry out both the operations of mixing the resin and expanding the shell.

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1~35~36 ' SUMMARY OF THE INVENTION
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In accordance with the present invention there is provided a rooE bolt assembly for securing a bolt in a bore hole having a bond-ing material therein that includes a bonding material adapted to the ,~, positioned in an unmixed condition in a bore hole. A rooE bolt with I, a threaded end portion has a camming plug with an internally threaded ;' bore and an outer surface threadedly engaged to the bolt threaded end ;, f portion. The canning plug is positioned to move axially on the bolt upon `` rotation of the bolt in a preselected direction. An expandable shell with a plurality of longitudinally extending fingers that have an inner surface and an outer surface is positioned with a portion of the inner surface of the fingers abutting a portion of the camming plug outer surface and a ,.~
portion of the inner finger outer surface adapted to engage the wall of the bore hole. The expandable shell fingers are arranged to expand outwardly to engage the outer surEace of the fingers to the wall of the bore hole by longitudinally movement of the canning plug relative to the bolt threaded end portion and the expandable shell. Means are provided for mixing at least a portion of the bonding material in the bore hole upon rotation of the bolt in a preselected direction in the bore hole while maintaining the expansion fingers in an unexpanded condition. Means . ,~ . .
f are also provided for moving the camming plug axially on the bolt threaded end portion and relative to the expandable shell fingers upon rotation of ''3 the bolt in the same preselected direction to expand the fingers and ;t'~,j ;~
anchor the bolt in the bore hole.
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~2~351~i Further in accordance with the present invention there is provided a method of anchoring a bolt in a bore hole including the steps of positioning a carnrning plug having an internally threaded bore and an outer surface into the upper portion of an expansion shell with a portion of the camming plug outer surface in abutting relation with a portion of the inner surface of a plurality of fingers extending upwardly from a lower ring portion of the expansion shell. The expansion shell is positioned on the threaded end portion of the bolt and threadedly engages the carnming plug to the end of the threaded portion of the bolt so that the camrning plug is movable longitudinally on the bolt threaded portion.
A bonding material is inserted into a bore hole. The bolt with the carnming plug threadedly engaged thereto is thereafter inserted into the bore hole. rlhe bolt is rotated in a preselected direction while the earning plug ris maintained in fixed relation with the expansion shell to thereby .. , , ~.~.
s mix at least a portion of the bonding rnaterial. Thereafter the bolt is rotated in the same preselected direction to move the carnrning plug on the i .
bolt to expand the fingers of the expansion shell and apply a tension to i;!l, ' the bolt ir. the bore hole.

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l l Prior Jo insertion of the expansion shell assembly ¦l and the bolt in the bore hole a suitable bonding material, such as an adhesive resin material, packaged in a breakable cart-l ridge, is inserted in the bore hole. The cartridye is advanced to the blind end of the bore hole by upward extension of the ¦ bolt with the expandable shell assembly attached to the bolt.
I Further upward advancement of the bolt fractures the cartridge, ¦¦ and thereafter the bolt together with the expansion shell Il assembly are rotated in a preselected direction to begin mixing i- 1l the components of the adhesive material that were separated I within the cartridge. Rotation of the bolt agitates the comyo-nents to interact and form a curable adhesive mixture.
'rhe stop means in one embodiment includes a shear-¦ able pin extending through a bore of the camrning plug. En portions of the pin are retained in aligned bores of the camming plug. The pin passes transversely through the bore of jl the plu`g that receives the threaded upper end of the bolt.
Preferably, the upper end of the bolt terminates in a reduced I diameter end portion formed by tapering the end of the bolt.
?.0 1l The bolt tapers to a preselected diameter determined by the diameter of the bolt and the type of shearable pin used. For example, a bolt having a dlsmeter of S/a inch is tapered at an I!

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11l ¦1 angle of about 45 degrees at the end ox the bolt, and the ¦¦ longitudinal length of the taper is about 1/4 inch. The tapered end of the bolt abuts the pin to yrevent initial ¦~ downward axial movement of the plug on the bolt during rotation of the bolt to effect mixillg of the adhesive components.
With the camming plug being restrained from downward movement on the bolt there is no relative rotation between the camming plug and the bolt. Thus the bolt, camrning pluq, and shell rotate as a single unit to effect mixing of the adhesive ~0 ¦ components in the bore hole. The curable mixture flows down-wardly into contact with the shell and camming plug and fills the voids between the shell and the wall of the bore hole. The presence of the shear pin prevents downward movement of the camming plug on the bolt for the period of time required to ¦ complete mixing of the resin components, For a quick setting-type of adhesive material expansion of the shell is delayed for about 20 to 30 seconds to permit complete mixing of the adhe-sive components before the shell is expanded.
~j As the adhesive mixture begins to harden around the '~0 ¦ shell and the camming plug, the mixture exerts a force upon the shell and camming plug resisting ro~a~ion of the shell and plug. When the torgue applied to the bolt exceeds a predeter-!l , 'i I

i j 2~35 ¦~ mined torque the anti-rotation forces exerted by the curing !¦ adhesiYe material exceed the material strength of the pin and ¦~ the pin fractures or is dislodged lrom the camrning pluy at the point of contact of the camming plug with the tapered end of I the bolt. The tapered configuration at the end of the bolt ¦¦ and abutting the pin assures dislodgement of the pin from the camming plug when the torque applied to the bolt exceeds a predetermined torque. The plug is then free to advance down-wardly on the bolt upon continued rotation of the bolt in the same direction for mixing to expand the fingers of the shell outwardly to grip the bore hole wall.
Il Expansion of the shell occurs after a preselected ll¦ time period of continued rotation of the bolt in one rotational ¦¦ direction. Thus the bolt is rotated in a single direction to ~j effect both mixing of the adhesive material and expansion of ¦I the bolt. This arrangement eliminates the need for reversing the direction of rotation of the bolt to expand the shell li after the adhesive material is mixed j ¦~ For an adhesive material of the quick setting resin-type, the mixed resin begins to harden within 20 seconds after rupture of the cartridge. The stop means in the embodi-I¦ ment of a shearable pin is constructed of a preselected mater-ial and has a preselected cross sectional area to control the ,1 c? it l 12~35~

material strength ot the pln. Thus the pin is opereble to fracture when the mixing stage is complete and before the resin mixture hardens. This assures that the shell will expand before the resin cures and after the resin is completely mixed.
For a selected resin system the pin is designed to fracture or shear in the bore of the camming plug when the torque applied to the bolt exceeds a predetermined torque. Preferably) the predetermined torque required to shear the pin is not reached until after, for example, the bolt is rotated for 2~ to 30 seconds, i.e., the period of time require for mixing the resin i components.
The stop means in one embodiment includes a pin fabricate of aluminum and having a preselected diameter. In another embodiment the stop means includes a steel pin havinq a length and diameter differing from that of the aluminum pin because of the difference in material strength of aluminum and steel. Further the location of the pin relative to the plug is ¦ selective, i.e it can be retained in a selected axial position in the plug and abuttinq the tapered end ox the bolt or it can be retained in the bolt only and abutting the bottom of the It plug. In each case by selecting the material composition and size ox the pin, as wel1 as, the position ot the pin, the li .

fracturing or shearing of the pin is controllable to meet the specifications of the resin system utilized. Thus a stop rneans is provided to permit mixing of the resin system for the period of time required for the selected resin system used before the shell is expanded upon continuous rotation of the bolt in one direction.
Further in accordance with the present invention there is provided a method of anchoring a bolt in a bore hole that includes the steps of threadedly engaging a carnming plug to the end of the bolt for axial movement thereon. An expand-able shell having a plurality of longitudinally extending fingers is positioned in surrounding relation with the camming plug on the bolt. Axial movement of the camming plug on the bolt is prevented by a stop means associated with the bolt upon rotation of the bolt in a preselected rotational direction.
The stop means is displaced by the bolt as the bolt continues to rotate in said preselected rotational direction when a torque in excess of a predetermined torque is applied to the bolt. Thereafter the camming plug is moved on the bolt upon displacement of the stop means to expand the fingers to anchor the bolt in the bore hole.

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jj Accordingly, the principal object of the present Il invention is to provide a method and apparatus for combining !I resin bonding and mechanical anchoring of a mine roof bolt in a rock formation by an expansion shell assembly provide with ¦ stop jeans that restrains expansion of the shell as the bolt is ¦ rotated in a preselected direction until a torque in excess of a predetermined torque is applied to the bolt to displace the stop means and permit expansion of the shell.
I Another object of the present invention is to proviae 1¦ a mechanical anchor for a mine roof bolt that is also adhesive-ly bonded within a bore hole where the bolt is continuously rotated in a preselected direction to pernlit the sequential operations ox mixing the resin material and thereafter expand-ing the shell after the resin is mixed but beiore it is cured to engage the wall of the bore hole.
A further object of the present invention is to provide a stop device associated with an expandable shell ¦ assembly that is operable to restrain the expansion of the shell for a period of time required to permit mixing of resin components in a bore hole where expansion of the shell is delayed until a preselected torque is applied Jo the bolt and ¦ j after the resin i6 mixed but before the resin is cured.

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An additional object of the prevent invention is to provide a roof bolt wi th a selectively dimensioned tapered end I portion operable to facilitate shearing of a stop device !~ associated with an expandable shell assembly after an initial period of rotation of the shell to mix a resin system sur- I
l rounding the shell where expansion of the shell is delayed ! until after the resin components are mixed.
These and other objects of the present invention will be more completely disclosed and described in the following l specification, the accompanying drawings and the appended I claims.

BRIEF r)ESCRIPTION GF THE DKAWINGS

Figure 1 is a fragmentary enlarged view in side elevation of an expansion shell assembly positioned on the threaded end of an elongated bolt, illustrating a stop devi.ce carried by a camming plug and engaging an upper end of the bolt for restraining movement of the plug on the bolt.
Figure 2 is a top plan view of the expansion shell assembly shown in Figure 1, illustratiny the stop device in the ~0 1¦ orm of a shearable pin extending through the bolt and having ¦ end portions retained in the camming plug.
Figure 3 is an enlarged fragmentary view in side elevation of the configuration of the threaded upper end of the bolt, illustrating a tapered end ox the jolt to facilitate shearing of the pin stop device.

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Figure 4 is a fragmentary exploded view of the expansion shell assembly of the present invention, illustratiny I! the shearable pin which is retained in a bore of the camming il plug and arranged to abut the tapered end of thy bolt.
Figure 5 is a fragmentary sectional view in side I
¦ elevation of the camming plug positioned on the bolt with the shell removed, illustrating the shearable pin extending throuqh the camming plug and abuttiny the tapered end of the bolt. I
I Figure 6 is a view similar to Figure 5, illustrating I, 3.0 1I the pin in a lower position in the camming slug and provided ,~ with parallel grooves on the opposite ends of the pin to Jo ;~ control shearing of the pin.
Figure 7 i6 a view similar to Figure 1, illustrating I, the stop device used with a bail-type expansion shell assembly.
I Figure 8 is a view similar to Figures 5 and 6 illu-! strating the shearable pin extending through the bolt only and jl, positioned in abutting relation with the lower end of the camming plug.
Figure 9 is a side elevation partially in section of I! the first step in the method of installing the root bolt in the ¦I bore hole, illustrating a resin cartridge in position at tne end Qf the bore hole for rupture by the expansion shell assem-¦ bly of the present invention.
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Figure l0 is a view similar to Figure 9, illustrating mixing of the components of the ruptured cartridge by rotation of the bolt with the stop device restraining downward movement of the plug during mixing.
Figure 11 is a vlew similar to Figures 9 and 10, illu-strating a further step of continuing rotation of the bolt in the same direction to fracture the stop device after the mixing ¦ step to permit the plug to advance downwardly on the bolt and ¦ expand the shell.
.~ ¦ Figure 12 is a view further illustrating the method ¦ of the present invention where the plug is advanced downward on the bolt to fully expand the shell fingers into engagement with the wall bore hole with the cured and hardened resin surrounding and embedding the expanded shell.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
i Referring to the drawings;and partlcularly to figures l1 1 and 4 there is illustrated an exuansion shell assembly I ¦I generally designated by the numeral 10 for securing a bolt 12 ~() I in a bore hole 14 drilled in a rock formation 16 (illustrated 1 in Figures 9-12) to support the rock formation 16 that overlies ¦ an underground excavation, a mine passageway, or the like. The bolt 12 3~

¦I has a threaded upper end portion 18 which i5 positioned i.n the ¦¦ upper blind end of the bore hole 14. The bore hole 14 i5 drilled to a preselected depth into the rock fonnation 16 as determined by the load bearing properties to be provided by the ! expansion shell assembly 10 and the bolt 12.
I ¦ The bolt 12 has an enlarged opposite end portion 20 as seen in F`igures 9-12 which extends from the open ena of I the bore hole 14. A roof or bearing plate 22 is retained by : ¦ the bolt enlarged end portion 20 on the end of the jolt 12.
¦ Further in accordance wittl the present invention a breakable cartridge 24 containing a conventional two component bonding material, such as disclosed in United States Patents 3,324,662 i and 3,394,5~7 is initially inserted in the bore hole 14 and I: advanced to the blind end of the bore hole 14, as shown in Figure 9, by upward advancement of the bolt t2 in the bore hole I: ! 14. Once the cartridge 24 is ruptured and the components ; ¦ thereof are mixed by rotation of the bolt 12 in a preselected direction, a stop device generally designated by the numeral 26 ; ` restrains expansion of the shell assembly 10 until the roof l¦ plate 22 is in abutting relation with the surface of the rock ;¦ formation 16 and the adhesive components are mixed, Il 124351~i 1 The bolt is continuously rotated in the same prese-lected direction for a period of time sufficient to complete mixing of the components of the bonding material The stop device 26 prevents expansion of the shell assembly 10 during ¦~ the mixing stage. The bolt continues to rotate in the same Il initial direction. When the torque applied to the bolt exceeds I ¦l a predetermined torque, as determined by the time for mixing the bonding material, the stop device 26 fractures. The !I expansion shell assembly 10 is then free to expand into grip-I ping engagement with the wall of the bore hole 14. The con-tinuous rotation of the bolt in the same initial direction completes the setting of the assembly 10. Thus the bolt is both mechanically anchored and adhesively bonded in the bore hole to prevent slippage of the expanded assembly 10 so that the bolt ¦¦ 12 remains tensioned to support the rock formation.
¦ Now referring in greater detail to the structure of j the expansion shell assembly 10 there is provided a shell member 28 conventional In design and including a solid ring ¦¦ end portion 30. The shell member 28 is expandable and has a ~0 ¦I plurality of longitudinally extending fingers 32 that extend axially from the ring end portion 30. Each of the fingers 32 ha a Iower end portion 34 connected to the ring end portion 30 1.1 I i I

3S~L6 Il , and an upper end portion 36. Longitudinally slots 38 (only one I, of which is shown in Figure 1) divide the fingers 32 from one another. Each of the slots 38 has a closed end portion 4 Il adjacent the ring end portion 30 and an open end portion 42 jl adjacent the upper end portion 36 of the respective finger 1! 32- 1 !

¦ Each finger 32 includes an outer gripping surface 44 and an inner smooth surface 46. The outer surface 44 includes I a gripping portion 48 that extends from the finger upper end jl portion 36 to a position spaced from the finger lower end ¦ portion 34. The gripping portion 48 of each finger 32 includes a series of spaced parallel, tapered horizontal grooves 50.
¦i The grooves 50 form a series of downwardly extending serrations ¦! that are operable upon expansion of the shell member 28 to ¦1 engage the wall of the bore hole 14 as the fingers 32 bend ¦l outwardly.
I The gripping portion 38 of each finger 32 is urged i into contact with the wall of the bore hole 14, as seen in ¦ figures 10 and ll, by a camming plug or wedge generally desig-on I nated by the numeral 52. The camming plug 52 includes a : ¦I threaded axial bore 54 threadedly engaged to the bolt threaded end portion lB. The camming plug 52 has a tapered configur-i, - 2~ -I

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¦ ation with an enlarged upper end portion 56 and a reduced lower ¦ end portion 58. A portion of the inner surface 46 of each finger 32 abuts a tapered planar surface 68 of the camming plug 1 52.
As illustrated in Figure 1, the camming plug 52 and I the shell member 28 are maintained in assembled relation on the ¦ bolt threaded end portion 18 prior to anchoring the assembly in the bore hole 14 drilled in the mine roof. Also as well known l in the art and illustrated in Figure 7, the camming plug 52 and the shell member 28 are connected by a yieldable strap or bail Il 60. The bail 60 is conventional and extends across the top ! of the camming plug 52. The bail 60 includes leg portions 62 that extend downwardly on opposite sides of the shell member 28. The leg portions G2 are positioned in a pair of opposed slots 64. The leg portions 62 terminate in in-turne~ end I¦ portions 66 that extend into the slots 64 and into engagement with the inner surface 46 of the shell member 2B. With this arrangement the bail 60 is engaged to the shell member 28 to malntain the camming plug 52 assembled within the shell member :?0 28.

Ij - 23 -l 1 l 3LZd~3516 ; As illustrated in Pi~ure 4, the camming plug 5 ! includes a plurality of tapered planar surfaces 68 divided from Il one another by longitudlnally extending grooves 70. As described above, the inner surface 46 of each finger 32 abuts a ¦¦ respective tapered planar surface 68. In one embodiment of the ¦¦ present invention as seen in Figure 5 the stop device 26 is , positioned in a bore 72 that extends through the camming plug 52 transversely to the threaded bore 54 of the camming plug l 52. As seen in Figure 5, the transverse bore 72 includes 11 opposite end portions 74 that extend through the plug 52 and ¦1 emerge through a pair of oppositely alignea grooves 7~ of the '1 plug 52.
jl Further as illustrated in Flgures l - 5, the stop : I device 26 includes a shearable pin 76 fabri.cated of a prese-lected yieldable material and having a preselected size and in the case of a circular pln, a yreselected diameter. The pin 76 is retained in the transverse bore 72 and includes respective end portions 78 and 80. The pin end portions 78 and 80 are retained in the bore end portions 74 of the plug 52 as illu-'I
n strated in the embodiment of the stop device 26 in Figures 1-7. The intermediate body portion of the pin 76 extends : transver~ ly through the plug longitudinal bore Si.

ii - 2~ -1 ~LZ~3516 Il The shearable pin 76 is selectively positioned to ¦l extend through the plug threaded bore 54 at a location to obstruct or prevent axial movement of the bolt threaded end ¦¦ portion 18 beyond a preselected depth into the camming plug bore 54. Thus upon initial assembly of the expansion shell assembly 10, the bolt threaded end portion lB is advanced into the camminy plug S2 until the bolt end portion 18 abuts the l shearable pin 76 and can advance no further into the camming I ¦l plug threaded bore 54.
ll The location of the transverse bore 72 through the camming plug 52 for positioning the shearable pin 76 is selec-: !j tive along the longitudinal length of the camming plug 52. To this end, as illustrated in Figure 5, the shearable pin 76 is positioned in the gemming plug transverse bore 72 at a location adjacent the plug upper end portion 56. In the embodiment of the present invention illustrated in Figure 6, the shearable pin 76 is positioned in a plug transverse Gore 82 locatecl adjacent the plug lower end portion 58.
j! With the embodiment illustrated in Figure 5 the ll length of the bolt threaded end portion 18 that extends into the camming plug bore 54 is less than that length when the shearable pin 76 iA retained ln the cammin~ pLug 52 adjacent !

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ll iL24;3516 the pluy upper end portion 56. In the position of the shear-¦ able pin 76 in the camming plug 52, as illustrated in Figure 6, ¦ the camming plug 52 is threaded on tl-e bolt 12 to engage only several of the threads on the bolt end portion l The inter-¦¦ mediate body portion of the shearable pin 76 prevents the bolt ¦¦ 12 prom passing any further into the camming plug threaded bore I1 54.
The material from which the shearable pin 76 isfabricated is selective, as for example, in one embodiment the '.0 pin 76 can be fabricated of 1/4 inch diameter steel; while, in l another embodiment it can be fabricated of 5/16 diameter ¦ aluminum. The type of material comprising the pin 76, as well i as, the dimensions and cross sectional area of the pin 76 are selective to control the shearing or fracturing of the pin depending upon the type of boning material utilized and the ¦ period of time required for mixing of the material components.
Ij Further to ensure shearing or fracturing of the stop device 26 11 before the curable mixture hardens a stop device, such as a steel pin 77 illustrated in Figure 6, is provided with defor-mations, such as longitudinally extending, parallel spaced ¦ grooves or recesses 84 positioned on the opposite end yortions 78 and 80 of the pin 77.

I

~243516 l'he material composition and structural design of the stop device 26, such a5 the pins 76 and 77 illustrated in Figures S and 6, are selected in accordance with the curing time of the particular type of bonding material utilized. For example with a commercially available quick setting type of resin system which begins to harden within 20 to 30 seconds or less following rupture of the cartridge 24 and mixing of the components, the size and material composition of the stop device Z6 are selected to permit fracture after 20 seconds or less of rotation of the bolt 12. Thus when the resin mixture begins to harden a force is applied to the assembly 10 tending to resist rotation of the shell member 28 and plug 52. The anti-rotational forces increase to a magnitude where the stop device 26 fractures.
Fracture of the stop device 26 occurs when the torque applied to the bolt 12 exceeds a predetermined torque. When the stop device 26 is no longer capable of resisting the anti-rotational forces of the adhesive material applied to the rotating shell assembly 10, the stop device 26 fractures or shears. Relative rotation between the camming plug 52 and the bolt 12 is no longer prevented. The camming plug 52 is then free to move downwardly on the bolt 12 as the bolt 12 continues to rotate in the same preselected rotational d.rection, I
!
l - 27 - I
1, Z43~;~6 The ability to control the shearing of the pin 76 l provides a versatile expansion shell assembly 10 operable for I use in combination with adhesive materials of varying curing characteristics, such as a quick setting-type resin curable I within 20 seconds or less of mixing or the type of aahesive ¦¦ material requiring 2 to 3 minutes of mixing before hardening begins. By selecting the material composition and cross sectional area of the stop device 26 in the form of a shear I! pin, as well as, the location of tbe shear fin relative to the I 1¦ camming plug SZ, e%pansion of the shell membee ~8 is prevented until after lapse of the time required to effect the necessary mixing of the adhesive components.
Once the curable mixture is formed and begins to l harden, the mixture exerts anti-rotational forces upon the camming plug 52 rotating with the bolt 18. When the shear pin is no longer capable of resisting these forces, the pin frac-tures or is dislodged from the camming plug 52 freeing the bolt jl 18 to rotate relative to the camming plug 52. This action , :
commences downward movement of the plug 52 and expansion of the ?0 I shell 28. Significantly, the entire operation is carried out j by continuoos rotation of the bolt 18 in the same or a single rotational direction. Preferably the shear yin fractures I! before the adhesive mixture completely solidlfies or hardens so ¦I that the expandable fingers 32 are movable outwardly into gripping engagement with the wall oE the bore hole i4.

ll l - ~8 ! I
Il I

lZ43~

I Now referring to Figure 3 there is lllustrated in greater detail the configuration of the threaded upper end 18 of the bolt 12. The bolt threaded upper end 18 terminates in a tapered end portion generally designated by the numeral 71.
The tapered end portion 71 15 tapered from the maximum diameter of the bolt 12 to a reduced diameter at the extreme end 73 of the bolt 12. The bolt tapered end portion 71 has a preselected dimension, that is, an angle A and a longitudinal ].ength .B.
¦ The magnitude of angle A and length B is selected as deter-I mined, for example, by the diameter of the bolt 12, the size and materlaI of the shear or stop device 26, the type of bonding material used, and the nature of the rock formation in Il which the bolt l is anchored. Thus with the above arrange-: ¦ ment, a cone frustum is formed at the threaded upper 18 of the I I bolt 12.
: For example in one embodiment of the present inven-I tion, à bolt 12 having a diameter of 5/8 inch is used in combination wlth a 1/4 inch diameter steel pin stop device 76.
The tapered end portion 71 has an angle A of 45 and a length ;~ of 1/4 inch. Thus the bolt 12 tapers from a 5/8 inch d1ameter to a 1/8 inch diameter at tbe extreme end 73 of the bolt 12.
i The extreme end 73 of the bolt 12 is flat and bears against the : ¦ pin 76.

I - 2~ -!l lZ~3516 ¦ The tapered end 71 of the bolt 12 applies a con-¦¦ centrated force upon a portion of the pin 76 as opposed to ¦ applying a force upon the full length of the portion of the pin 76 t)lat is positioned in the plug bore 54. By tapering the I bolt end portion 71 in accordance with the above example, a l ¦ inch section of the bolt extreme end 73 abuts the pin 76 rather than the full S/B inch diameter of the bolt 12. This ensures breaking the pin 76 or dislodging the pin 76 from a position in the plug bore 54 obstructing downward movement of the plug 52 ~0 ¦ when a preselected torque is applied to the bolt 12 after I mixing of the bonding components is complete As stated the dimensions A and B of the bolt tapered Il end portion 71 are selected to meet the specific circumstances I and conditions for the type of expansion shell assembly 10 and Il bolt 12 used with a partic~alar bonding material. For example, I

¦ the tapered end portion 71 can be provided with an angle A that varies~in the range between about 15 to 65 and a lenyth B
Il that varies in a range corresponding to the angle A. However, ¦I regardless of the selected dimensions of the taper angle A and I length B, the presence of the tapered end portion 71 on the bolt 12 facilitates removal of the pin 76 from a position in ¦ the plug bore 54 obstructing downward movement of the plug 52 ¦1 on the bolt 12 by concentrating the upward thrust exerted by ¦¦ the bolt 12 on a portion of the pin 76.
Il f 2~ 51`~

I A further embodiment of the shear device 26 is ¦ illustrated in Figure I. In this embodiment a shear pin j 79 is retained solely in a bore 86 extending transversely I through the threaded end portion lB of the bolt lZ adjacent the tapered end portion 71:thereof. The shear pin 79 includes an ¦ intermed1ate portion~81 retained in the transverse bore 86 and a pa1r of opposite end port1on 83 and 85. The pin end portions :: ~3 and 85 extend outward1y from the bore 86 and in the assembly ¦ lO are positioned opposi;tely of;a pair of slots 3~ between 2.0 ! adjacent shell fingers:32. The camming plug 52 is advanced I I! downwardly on the bolt Ullti]. the lower end portion 58 of the 11 plug 52 abuts the pin end portions 83 and 85. The pin end portions 83 and 85 abutting the camming plug 52 pre:vent further :~ downward movement of the ~camm1ng plug 52 on the bolt 12.
: As with the above described embodiments of the: stop device 261tt1e shearable p1n 79 resists relative rotation between: the~bolt 12~ and the ~camm1ng plug 52 unt11 a torque in excess of a predetermined tarque is applied to the end of the : bolt. :At this torque the resistance offered` by t:he curable ; ~20 bond1ng~mixture to rotation of the plug:52 results 1n fractur-inq oL thy pin 79. the p n 79 is des1gned so that it does not Il j - 31 -.

351~

fracture until the mixing of the bonding materials is complete and the mixture begins to harden. The pin end portions 83 and Y5 break off from the intermediate portion 81 and are free to move through the shell slots 38.
When the torque for breaking the pin 79 is reached, the mixing is complete. The pin 79 breaks permitting downward movement of the camming plug 52 to expand the shell member 28.
Expansion of the shell member 28 is delayed until the bonding 1 material is mixed but not after the mixture rigidifies in the 1I bore hole 14.
j It should also be understood that the stop device 26 includes any suitable device that restrains axial movement of ¦ the plug 52 on the bolt 12 beyond a preselected point on the threaded end portion 18 of the bolt 12, as for example, an ¦ obstruotion member suitably retained in the plug threaded bore I 54, The obstruction member is operable to restrain relative rotatlon between the bolt 18 and the plug 52 until a pre-selected torque is applied to the bolt 18. before the prese-lected torque is applied, the bonding material is mixed.
When a torque in excess of the preselected torque is applied, the obstruction member is either broken or displaced in the 'I
lil I

! 32 -I i - -!

plug bore 54 to the extent permittting relative rotation between the bolt 18 and the plug 52 permitting downward move-ment of the plug 52 on the bolt. This results in expansion of the shell member 28 and anchoring of the assembly l in the bore hole lo.
The top device 26 in another embodiment can include an obstruction which is not required to break or shear before expansion of the shell member 28 begins. This type of stop device 26 can include a flexible member, such as wire or the like, having end portions secured to the camming plug 5~ and extending through the plug bore 54 obstructing the path of the rotating bolt 18. The wire abutting the extreme end 73 of the bolt tapered end portion 71 prevents downward movement of the plug 52 on the bolt l8. Movement of the plug 52 is re-strained until the anti-rotational forces of the bonding mixture applied to the plug 52 result in yielding or bending of the wire permitting downward movement of the plug 52 on the bolt 12 upon continued rotation of the bolt 12. The applica-tion of the torque which results in bending of the wire corres-ponds to the formation of a curable bonding mixture and the initiation of expansion of the she1l me-bcr 28.

!l -It li z~3~

Now referring to Figures 9 - 12, there is illustrated I the method of anchoring the apparatus l and the bolt 12 in the bore hole 14 of the rock formation 16. Initially, as illustra-ted in Figure 9, the resin cartridge 24 is inserted in the hole 14 drilled in the mine roof or rock formation 16 by upward :1 advancement by the bolt 12 with the apparatus 10 attached to : I the threaded end portion 18 of the bolt 12. The cartridge 24 : : I is pushed to substantially the blind end of the bore hole 14.
With the cartridge 24 inserted ln the upper part of the bore : Jo j hole 14, as illustrated ;in Figure 9, the bolt 12 is thrust 1¦ upwardly to rupture of the cartridge 24, : Thereafter, the entire assembly 10: is rotated in a preselected direction as indicated by the arrow in Fiyure 9 by : ¦ applying a torque to the~bolt enlarged end portion 20. The stop device 26 in the form of the shear pin 76 illustrated in Figures 9 - 12, fabricated of; a preselected material and of a preselècted size prevents relative~rotation between the camming plug~52 and the bolt 12:during the initial~rotation of the bolt j : 12 to rupture the cartridge and mix the resin components. In 201 this manner the camming pluge 52~is restrained from moving downwardly on the bolt:12 by the bolt tapered end portion 71 l : I abutting the shear pin 76 during the initial rotation of the bolt 12.

~j l! l I, - 34 - .

12g~51~ 1 Rotation of the bolt 12 effects mixing of the resin ¦I components which are released from the cartridge 24 when the ¦ cartridge 24 is ruptured. Preferably the resin components include a thermoplastic resin and a catalyst. As the bolt Il lZ is rotated the resin and the catalyst are mixed to form ¦¦ a curable resin mixture ~8. The resin mixture 88 by virtue ¦ of its thixotropic characteristics is retained within the ¦ bore hole 14. To effectiYely retain the volume of the mixture ~8 in surrounding relation with the assembly 10 a suitable ~0I device, such as a washer 9~, is retained on the bolt 12 I adjacent the bolt threaded end portion l The washer 90 has a ¦ diameter sufficient to permit the washer to move freely in the bore hole 14 with the bolt 12 into position. In one embodi~
¦¦ ment, the washer 90 is fabricated of metal and may be either I welded or press fit on the bolt 12 spaced a preselected dis-tance below the bolt threaded portion 18. In another embodi-¦ ment the washer 90 is fabrlcated of an elastomeric material.
l The elastomeric washer 90 is retained in gripping engagement I on the bolt 12 below the threaded end portion 18.
~nThe resin mixture 88 poIymerizes at room temperature, ; i.e. a temperature in the range between about 40 to ~0 F.
The bolt 12 is rotated continuously in the direction inaicated by the arrow in Figure 10 to effect mixing of the resin. The shear pin 76 abutting the extreme end 73 of the bolt tapered . I, I .
I

l - 35 -

4~

¦ rotation between the camming plug 52 and the bolt 12. This ¦ prevents the camming plug 52 from moving downwardly on the bolt 12 until the mixing of the resin components is complete The period of time for mixing a quick setting-type resin is l generally between about 20 to 3~ seconds. During the mixing i stage as seen in Figure 10 the bolt 12 is held in position I within the bolt hole 14 with the roof plate 22 abutting the rock formation 16 around the open end of the bolt hole 14.
I The shear pin 76 by restraining downward movement of I the camming plug 52 on the bolt 12 ensures complete mixing of the resin cornponents before the sheil 2B is expanded. However, it due to the shear characteristics of the pin 76 designed ¦¦ for the resin system utilized, the shell 2~ expands before the ll resin mixture 88 completely hardens around the shell member ¦1 28. From the time the cartridge 24 is ruptured, the bolt 12 is i continuously rotated in one direction only, i.e. either ~j clockwise or counterclockwise, to mix the resin components, as well asj expand the sheIl member 2B. As the bolt 12 rotates ¦ the curable resin mixture 88 slows into the fissures and faults of the rock formation 16 surrounding the bore hole 14. In this well known manner, the rock strata are adhesively united to further f nforce the rock formation.

Il I

Il Il ~L2~3~
After the mixing stage, resin mixture 88 begins to cure or harden in the bore hole 14. As the resin mixture 88 begins to harden it exerts forces on the rotating shell member 28 and the camming plug 52 resisting their rotation. At a pre-determined torque applied to the bolt 12, which is reached after a elapse of time to complete the mixing, the material strength of the shear pin 7~ is exceeded by the anti-rotational forces exerted by the resin mixture 88 and the pin 76 fractures or shears. Consequently, the intermediate portion of the pin 76 in the plug bore 54 abutting the bolt tapered end:portion 71 is bent and broken off from the pin end portions 78 and ~0 whlch are retained in the plug, as seen in Figure 11. This permits the pin 76 to be displaced in the camming plug bore 54 so that the plug 52 is free to Jove downwardly on the bolt threaded end portion l8.
Referring to Figure 11, downward movement of the camming~plug 52 on the bolt 12, upon rotation of the bolt 12 in the same direction for forming the resin mixture 8~, expands the shell member 28. The fingers 32 are bent outwardly about the shell ring end portion 30 to move the outer gripping surfaces 34 lnto gripping engagement with the wall of the bore hole l4. The rotation of the bolt 12 is continuous in the Il ~2~3516 direction indicated by the arrows in Figures 10 and 11 through the resin mixing and shell expanding stages. Rotation of the bolt 12 continues until a preselected torque is applied to the bolt 12. When the preselected torque is applied, the shell member 28 is fully expanded and the gripping portions 48 of the fingers 32 are embedded in the rock formation to securely anchor the bolt 12 in the bore hole 14.
When the shell member 28 is expanded the resin mixture 88 is cured. By anchoring the bolt 12 in the bore hole 1 14 by the expansion shell member 28, the bolt 12 is tensioned.
The addition of the cured resin in sorrounding relation with the bolt 12 and the expanded shell member 28 prevents slippage of the shell member 28 in the bore hole 14. Tension on the bolt is thus maintained and is not reduced by slippage of the expanded shell member 28 in the bore hole.
By the provision of the stop device 26, the expansion shell assembly 10 is operable as a mixing tool to admix the components of the resin cartridge 24 to form the curable mixture 88 before the shell member 28 is expanded. The stop device 26 prevents downward movement of the camming plug 52 on the bolt 12 during the period in which the resin components are mixed. Also by the provision of the stop device 26, the bolt ~35 i 12 is continuously rotated in the same preselected direction to¦¦ effect both mixing of the resin components and expansion of the shell member 2~. Thus it i5 not necessary with the present invention to rotate the bolt 12 in a first direction to ¦ effect mixing of the resin components and then followed by I reversal of the direction of rotation of the bolt 12 to effect ! expansion of the shell member 28.
I The provision of the stop device 26 associated with ¦ the camming plug 52 substantially improves the efficiency and In ¦ ease of installation of a roof bolt that is both mechanically I anchored and resin bonded within a bolt bore hole. It should also be understood even though the direction of rotation for il both mixing the resin components and expanding the shell member I¦ ~8 is illustrated in a counterclockwise direction in figures 11 I¦ and 12, the direction of rotation can be clockwise as well ¦ depending upon whether the bolt end portion 18 is left-hand threadeù or right-hand threaded.
According to the provisions of the patent statutes, I
have explained the principle, preferred construction and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiments. How-ever, it should be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrateù and described.

.

'i

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS DEFINED AS FOLLOWS:

1. A bolt assembly to be secured in a bore hole, said bolt assembly including a bonding material positioned in said bore hole in an unmixed condition, a bolt having a threaded end portion, a cam-ming plug having an internally threaded bore and an outer surface, said camming plug threadedly engaged to the threads adjacent the end of said bolt threaded end portion, said camming plug positioned to move axially on said bolt upon rotation of said bolt in a preselected direction, an expandable shell having a plurality of longitudinally extending fingers, each of said fingers having an inner surface and an outer surface, a portion of each of said inner surfaces abutting a portion of said camming plug outer surface an a portion of each of said finger outer surfaces being arranged to engage the wall of said bore hole by longitudinal movement of said camming plug relative to said bolt threaded end portion and said expandable shell, means for mixing at least a portion of said bonding material in said bore hole upon rotation of said bolt in said preselected direction in said bore hole while maintaining said expandable shell in an unexpanded condition, and means for moving said camming plug axially on said bolt threaded end portion and relative to said expandable shell fingers upon rotation of said bolt in said same preselected direction to bend said fingers outwardly and anchor said bolt in said bore hole.

2. A bolt assembly as set forth in claim 1 in which said bond-ing material includes a cartridge of bonding material in an unmixed condition positioned in said bore hole.

3. A bolt assembly as set forth in claim 2 in which said camming plug positioned on the end of said bolt threaded end is arranged upon insertion of said bolt in said bore hole to fracture said cartridge and permit said unmixed bonding material to flow downwardly in said bore hole around at least a portion of said bolt, camming plug and expandable shell.

4. A bolt assembly as set forth in claim 1 which includes, means for applying a tension to said bolt upon further rotation of said bolt in said same preselected direction and anchoring said bolt in said bonding material to maintain said tension on said bolt.

5. A bolt assembly to be secured in a bore hole, said bolt assembly including a bonding material positioned in said bore hole in an unmixed condition, a bolt having a threaded end portion, a camming plug having an internally threaded bore and an outer surface, said camming plug threadedly engaged to the threads adjacent the end of said bolt threaded end portion, said camming plug positioned to mo~e axially on said bolt in a direction away from said end of said bolt threaded end portion upon rotation of said bolt in a preselected direc-tion, an expandable shell having a plurality of longitudinally extending fingers, said fingers each having an inner surface and an outer surface, a portion of each of said finger inner surfaces abutting said camming plug outer surface and a portion of each of said finger outer surfaces arranged to bend outwardly and engage the wall of said bore hole by longitudinal movement of said camming plug relative to said bolt threaded end portion and said expandable shell, and means for mixing at least a portion of said bonding material in said bore hole upon rotation of said bolt in said preselected direction in said bore hole while maintaining said camming plug fixed relative to said expandable shell, and means for moving said camming plug axially on said bolt threaded end portion and relative to said expandable shell fingers upon rotation of said bolt in said same preselected direction to bend said fingers outwardly and anchor said bolt in said bore hole.

6. A bolt assembly as set forth in claim 5, which includes, means for applying a tension to said bolt upon further rotation of said bolt in said preselected direction and anchoring said bolt, expansion shell and camming plug in said bonding material, and said bonding material arranged to prevent rotation of said bolt in said camming plug in a direction opposite to said preselected direction.

7. A bolt assembly to be secured in a bore hole, said bolt assembly including a bonding material positioned in said bore hole in an unmixed condition, a bolt having a threaded end portion, a camming plug having an internally threaded bore and an outer surface, said camming plug threadedly engaged to the threads adjacent the end of Said bolt threaded end portion, said camming plug positioned to move axially on said bolt upon rotation of said bolt in a preselected direc-tion, an expansion shell having a lower ring portion and a plurality of fingers extending upwardly therefrom, said fingers each having an inner surface and an outer surface, a portion of each inner surface abutting said camming plug outer surface and a portion of each outer surface arranged to bend outwardly and engage the wall of said bore hole, said expansion shell positioned on the threaded end portion of said bolt and engaging said camming plug, means for mixing at least a portion of said bonding material in said bore hole upon rotation of said bolt in said preselected direction in said bore hole while maintaining said camming plug fixed relative to said expansion shell, and means for moving said camming plug on said bolt upon further rotation of said bolt in said preselected direction to bend the fingers of said expansion shell out-wardly and apply a tension to said bolt in said bore hole.

8. A bolt assembly for securing a bolt in a bore hole having a bonding material therein set forth in claim 7 in which, said expansion shell is adapted to be connected to said bolt solely by means of said camming plug.

9. A bolt assembly for securing a bolt in a bore hole having a bonding material therein as set forth in claim 7 in which, said expansion shell ring portion includes an inner cylindrical surface positioned around said bolt with an annular space between said bolt and said expansion shell ring portion inner cylindrical surface.

10. A bolt assembly to be secured in a bore hole, said bolt assembly including a bonding material positioned in said bore hole in an unmixed condition, a bolt having a threaded end portion, a camming plug having an internally threaded bore and an outer surface, said camming plug threadedly engaged to the threads adjacent the end of said bolt threaded end portion, said camming plug positioned to move axially on said bolt upon rotation of said bolt in a preselected direction, an expansion shell having a lower ring portion and a plurality of expansion fingers extending upwardly therefrom, said fingers each having an inner surface and an outer surface, a portion of each inner surface abutting said camming plug outer surface and a portion of each outer surface arranged to bend outwardly and engage the wall of said bore hole, said expansion shell positioned on the threaded end portion of said bolt and engaging said camming plug, means for mixing at least a portion of said bonding material in said bore hole upon rotation of said bolt in said preselected direction in said bore hole while maintaining said expandable shell in an unexpanded condition, and means for moving said camming plug on said bolt upon further rotation of said bolt in said preselected direction to bend the fingers of said expansion shell outwardly and apply a tension to said bolt in said bore hole.

11. A bolt assembly for securing a bolt in a bore hole having a bonding material therein as set forth in claim 10 in which, said expansion shell is adapted to be connected to said bolt solely by means of said camming plug.

12. A bolt assembly for securing a bolt in a bore hole having a bonding material therein as set forth in claim 10 in which, said ex-pansion shell ring portion includes an inner cylindrical surface position-ed around said bolt with an annular space between said bolt and said expansion shell ring portion inner cylindrical surface.